1. Acute Renal Failure in the Intensive Care Unit Ana Lia Graciano, MD Pediatric Critical Care The University of North Carolina-Chapel Hill

2. Basic Renal Physiology

4. renal parenchyma cortex medulla nephrons cortical juxtamedullary structural organization

9. Adjusting the resistances of the afferent and efferent arterioles, the kidneys can regulate both the hydrostatic pressures in the glomerular and peritubular capillaries, changing the rate of glomerular filtration and/or tubular reabsorption in response to homeostatic demands.

10. determinants of Glomerular Filtration Rate (GFR) Glomerular hydrostatic pressure Glomerular colloidosmotic pressure Bowman’s capsule pressure net filtration pressure: hydrostatic + colloid osmotic pressure

12. autoregulation a feedback mechanism that keeps renal blood flow (RBF) and glomerular filtration rate (GFR) constant despite changes in arterial blood pressure.

14. afferent arteriolar resistance - + Proximal tubule NaCl reabsorption Macula densa feedback mechanism for autoregulation afferent arteriolar resistance arterial pressure Glomerular hydrostatic pressure GFR macula densa NaCl renin angiotensin II efferent arteriolar resistance

19. major sites of solute and water movement across the nephron

20. Acute Renal Failure (ARF)

21. acute renal failure: definition ARF is an abrupt decline in glomerular and tubular function, resulting in the failure of the kidneys to excrete nitrogenous waste products and to maintain fluid and electrolyte homeostasis.

23. acute renal failure: pathophysiology Increase in NaCl delivered to macula densa. Damage to proximal tubule cells increases NaCl delivery to distal nephron,. This causes disruption of feedback mechanism. Obstruction of tubular lumen. Casts (necrosis of tubular cells and sloughed basement membrane) clog the lumen. This will increase the tubular pressure and then GFR will fall. Backleak of fluid through the tubular basement membrane.

29. Prerenal azotemia and ischemic tubular necrosis represent a continuum. Azotemia progresses to necrosis when blood flow is sufficiently compromised to result in the death of tubular cells. Most cases of ischemic ARF are reversible if the underlying cause is corrected.

34. renal indices Renal Failure Index (RFI) RFI: urine [Na] urine creatinine / serum creatinine

35. renal indices Fractional Excretion of Na (FENa) FENa: [ urine Na/serum Na] x 100 % [urine creatinine/serum creatinine]

38. urine and serum laboratory values